Method for producing novel leather substitutes



United States Patent 3,169,885 NETHOD FOR PRQDUCENG NOVEL LEATIER SUBSTITUTES Marcos M. Golodner, West Orange, N.J., and George E.

Sabine, Bronx, N.Y., assignors to Interchemical Corporation, New York, N.Y., a corporation of Ohio No Drawing. Filed Mar. 15, 1963, Ser. No. 265,339 18 Claims. (Cl. 117135.5)

This invention relates to a novel breathable coated fabric which provides an excellent leather substitute having both the hand or feel of leather and water vapor transmission or breathability of leather.

A good leather substitute should have several basic qualities; 1) a hand like that of leather, (2) a breathability of leather, (3) a good tear strength or resistance to tearing and (4) its top or exposed surface should have no visible pores.

Copending application S.N. 262,813 entitled A Novel Leather Substitute and Method for Producing the Same, filed on or about January 7, 1963, in the name of Norman J. Bertollo is directed to a novel coated fabric which is quite similar to leather in the aforementioned properties. The disclosure of said application is hereby incorporated into and made a part of the present application.

The novel coated fabric of the copending application comprises a textile substrate, which may be a woven or a non-woven textile, carrying a porous polymeric coating comprising the polyesterurethane elastomers described in Us. Patent 2,871,218. The porous coating has dispersed therein a flock.

Said copending application is directed to a method of production of said novel coated fabric which entails dissolving the polyesterurethane of Patent No. 2,871,218 in a suitable solvent, preferably methyl ethyl ketone or tetrahydrofuran. Cyclohexanone may also be used as a solvent. Preferably the polyesterurethane is used as a 20% to 35% solution and most preferably as a 25% to 30% solution.

The solution of the polymeric material is mixed with water to form a dispersion to which the flock is added and dispersed. Preferably, the water added is about from 5% to 30% of the Weight of the solvent present and most preferably is from to of the Weight of the solvent. Preferably the weight of the flock used is equal to about from 10% to and most preferably from 20% to 25 of the weight of the polyesterurethane employed. According to the process of said copending application, the water preferably contains colloidal magnesium aluminum silicate.

Further, in accordance with the teaching of said application, the coating composition is then applied to the substrate at a wet coating thickness preferably from about to 150 mils. The substrate is either a woven or nonwoven textile. The coated fabric is then leached in cold water, having a preferred range of 12 to 20 C. and then air-dried:

We have now discovered improvements in the basic process of the copending application which results in the production of a leather substitute having a hand and appearance much closer to that of leather and a breathability at least equal to that of leather.

We have found that breathability may be significantly enhanced if the water being dispersed in the solution contains carboxymethyl cellulose or a natural gum such as gum tragacanth, gum arabic or gum karaya in place of the colloidal magnesium aluminum silicate used in the process of the copending application. This gum preferably equals from 2 to 10% of the weight of the polyesterurethane in the dispersion. (It should be noted that in "ice Suitable surfactants include alkyl aryl polyether alcohol types such as as well as sorbitan oleates such as sorbitan trioleate. Best results are achieved when the surfactant used is polyoxyethylene sorbitan mono-oleate. This surfactant is believed to have plasticizing and other effects in addition to its effects as a surfactant. When present the polyoxyethylene sorbitan monoleate preferably equals from 10% to 40% of the polyesterurethaneweight.

We have also found that both breathability and hand of the leather-substitute may be greatly improved by using leaching times and temperatures quite different from those described in said copending application. In the process of the copending application, leaching is carried out at temperatures in the range of 12 to 20 C. for about 15 minutes. We have found that when leaching at such low temperatures, best results are obtained by using a leaching time of about 9 to 16 hours. When using shorter leaching times e.g., in the order of 10 minutes to 3 hours, we have found that it is important to employ hot water e.g., at temperatures of from 40 to 60 C. Excellent results are also obtained when the leaching is conducted in part with hot water and in part with cold water, e.g., 1 to 3 hours at 15 C. to 18 C. and 1 to 3 hours at 40 to 45 C.

After leaching is completed, the coated fabric is permitted to dry, suitably by air drying. However, the drying may also be conducted at higher temperatures.

It should also be understood that the coated fabrics of this invention may be further overcoated with top coats which do not appreciably reduce water vapor transmission.

For optimum results, particularly with respect to breathability, the pH of the coating composition should be from 5.5 to 7.5 and most preferably 6 to 7.

Because of the agitation necessary to form the aforementioned dispersions, there is a tendency for pockets of air to become trapped. Such air pockets tend to form voids in the final coating on the fabric. In order to avoid these effects it is often desirable to deaerate the coating dispersions prior to application on the substrate. This may be readily accomplished by conventional methods such as vacuum pumping.

It has been further found that when using the improved process of this invention leather substitutes may be prepared using vinylidene chloride-containing copolymers in place of the polyesterurethane elastomers. The vinylidene chloride-containing copolymers preferably contain more than 50% of vinylidene chloride and most preferably more than In addition to' the vinylidene chloride component, these copolymers usually contain acrylonitrile,

vinyl chloride or vinyl acetate.

The following examples will illustrate the practice of this invention: 5

Example I A polyesterurethane is prepared following the procedure set forth in US. Patent 2,871,218, col. 4, lines 13 to 27. A mixture of 1447 g. (1.704 mols) of hydroxyl poly (tetramethylene adipate), molecular weight 849, hydroxyl number 130.4, acid number 0.89, and 109.6 g. (1.218 mols) of butanediol-L4 is melted in a four liter kettle and stirred with a spiral ribbon stirrer for about 20 minutes at a pressure of 5 to 6 mm. at to C. To this mixture, there is added 730 g. (2.92 mols) of difor about 1 minute and is then poured into a lubricated one gallon can which is promptly sealed with a friction top and the can placed in a 140 C. oven for 3.5 hours. The product is then cooled. 1 a

In 100 parts of a solution of said product polyesterurethane in methyl ethyl ketone (28% ,solidsby weight), there are dissolved 5.6 parts of polyoxyethylene sor-bitan monooleate (marketed under the trademark Tween 81) 16 parts of a 6% aqueous solution of gum tragacanth are added to the solution and the mixture is stirred to form a dispersion which is creamy light tan in color. To the resulting mixture, there is added about 6 parts of a rayon flock having an average fiber length of about .03 inch and the mixture is then deaerated by the application of a partial vacuum of 400 mm. for about minutes while continually stirring. The mixture is coated at a thickness of /8 inch onto a cotton sheet having a. weight of 0.002 ounce per square inch. As soon as possible after coating, the coated fabric is leached with water. This is accomplished, for example, by placing a piece of coated fabric 1.5 sq. ft. in area in a tank containing about 2 gallons of water and then flowing water at about 16 to 20 C. through the tank at the rate of about 6 of a gallon a minute to replace the water in the tank. The leaching is continued for 16 hours. The resulting coated fabric after air drying at room temperature has a hand closely resembling that of a leather and a water vapor transmission or breathability approaching that of leather. Water vapor transmission when measured according to ASTM-E96-53T shows that the water vapor transmission of the product is about 90 g./square meter/ 24 hours at a 100% relative humidity and a temperature of 100 F. while natural leathe has a water vapor transmission of from about 80 to 150 g./ square meter.

The example is then repeated using gum arabic with substantially the same results as with the gum tragacanth which is replaced except thatthe water vapor transmission is in order of 50 g./ square meter/'24 hours.

The example is then repeated twice using carboxymethyl cellulose and gum karaya respectively. The results are about the same as 'Wlth gum tragacanth.

Example Il Example, I is repeated using the same ingredients, proportions and conditions except that the leaching step is conducted atja temperature of 60 F. for a period of 30 minutes. The water vapor transmission is about 50.

Example III Example I is repeated using the same ingredients, proportions and conditions except that the leaching is carried out for about 2 hours at a water temperature of 17 -19 C; and continued for another 3-hours at a 42-47 C. water temperature. The resulting coated fabric has about the same hand as that of Example I. The fabric has a water vapor transmission of about 110 according to ASTM- E96- 53T. I V e V Example IV Example III is repeated using the same ingredients, proportions and conditions except that in place of the polyesterurethane used in Example III, a polyesterurethane made in accordance with the description set forth in US. Patent 2,871,218, col. 5, lines 19-28, is used. The resulting coated fabric has properties *very close to those described for the product of Example I.

i .Example V In 100 parts of a solution of a copolymer'of 85% vinylidene chloride and 15% aorylonitrile in methyl ethyl ketone (41% solids content by weight), there is dissolved Sparts of polyoxyethylene sorbitan monooleate. '30 parts of a 6% aqueous solution of colloidal magnesium alumi num silicate are added to the solution and the mixture is stirred to form a dispersion. To the resulting dispersion,

there is added about 6 parts of a rayon flock having an average fiber length of about .03 inch and the mixture is stirred to evenly disperse. the flock. The dispersion is then coated in accordance with the procedure of Example III and the resulting coated fabric is leached in accordance The water vapor;

with the procedure of Example III. transmission is almost equivalent to that of Example III 7 and the hand is almost as good as that of the fabric of Example III.

.While there have been described what is at present considered'to be the preferred embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed to cover all such changes and modifications as fall within the true spirit and scope of the invention.

7 What is claimed is:

l. A method for making a water vapor permeable coated fabric comprising dispersing (A) flock in a mixture of (B) Water having dissolved therein a member selected from the group consisting of carboxymethyl cellulose,

gum arabic, gum tragacanth and gum karaya and (C) a solution in a'solvcnt, selected from the group consisting of methyl ethyl ketone, tetrahydrofuran and cyclohexanone, of an essentially linear polyesterurethane elastomer which is'the reaction product obtained by heating a mixture comprising as essential polyurethane ingredients (1) one mol of an essentially linear hydroxyl terminated polyester oia saturated aliphatic glycol having from 4 to 10 carbon atoms and having hydroxyl groups on its terminal carbon atoms and a material selected from the group consisting of a dicarboxylic acid of the formula V I, nooc- -a coon where R is an alkylene radical containing from 2 to 8 carbon atoms and its anhydride, said polyester having an average] molecular weight between 600 and 1200 and having an acid number less than 10, and (2) from 1.1 to 3.1 mols of a diphenyl diisocyanate'having an isocyanate group on each phenyl nucleus in the presence of (3) from about 0.1 to 2.1 mols of a saturated aliphatic free glycol containing from 4 to 10 carbon atoms and having hydroxyl groups on its terminal carbon atoms, the molar amount of said polyester and said free glycol combined being essentially equivalent to the molar amount of said diphenyl diisocyanate whereby there are essen',- tially no groups of the class consisting of isocyanate and hydroxyl groups in said reaction products, then applying said dispersion to the surfaces of a'textile substrate and leaching said coated textile with water to remove the solvent.

2. The method of claim 1 wherein the polyester.- urethane solution further contains polyoxyethylene sorbitan monooleate. p a

3. The method of claim 1 wherein the substrate is a cotton fabric. V

4. The method of claim 1 wherein said member dis solved in the water is gum tragacanth. V

' 5. The method of claim 1 wherein said member dis solved in the Water is gum arabic.

oxyethylene sorbitan monoleate and an essentially linear polyesterurethane elastomer which is the reaction product obtained by heating a mixture comprising as essential polyurethaue'ingredients (1) one mol of an essentially linear hydroxylterminated polyester of a saturated aliphatic glycol having from 4 to 10 carbon atoms and having hydroxyl groups on its terminal carbon atoms and val a material selected from the group consisting of a dicarboxylic acid of the formula where R is an alkylene radical containing from 2 to 8 carbon atoms and its anhydride, said polyester having an average molecular weight between 600 and 1200 and having an acid number less than and (2) from 1.1 to 3.1 mols of a diphenyl diisocyanate having an isocyanate group on each phenyl nucleus in the presence of (3) from about 0.1 to 2.1 mols of a saturated aliphatic free glycol containing from 4 to 10 carbon atoms and having hydroxyl groups on its terminal carbon atoms, the molar amount of said polyester and said free glycol combined being essentially equivalent to the molar amount of said diphenyl diisocyanate whereby there are essentially no groups of the class consisting of isocyanate and hydroxyl groups in said reaction products, then applying said dispersion to the surface of a textile substrate, leaching said coated textile with water to remove the solvent and drying the coated fabric.

9. The method of claim 8 wherein said dispersion is deaerated prior to being applied to the substrate.

10. The method of claim 1, wherein the coated textile is leached at a temperature above 40 C.

11. A coating composition comprising flock dispersed in a mixture of water having dissolved therein a member selected from the group consisting of carboxymethyl cellulose, gum tragacanth, gum karaya and gum arabic and a solution in a solvent, selected from the group consisting of methyl ethyl ketone, tetrahydrofuran and cyclohexanone, of polyesterurethane elastomer produced by heating a mixture comprising as essential polyesterurethane forming ingredients (1) one mol of an essentially linear hydroxyl terminated polyester of a saturated aliphatic glycol having from 4 to 10 carbon atoms and having hydroxyl groups on its terminal carbon atoms and a material selected from the group consisting of a dicarboxylic acid of the formula HOOCR--COOH where R is an alkylene radical containing from 2 to 8 carbon atoms and its anhydride, said polyester having an average molecular weight between 600 and 1200 and having an acid number less than 10, and (2) from about 1.1 to 3.1 mols of diphenyl diisocyanate having an isocyanate group on each phenyl nucleus in the presence of (3) from about 0.1 to 2.1 mols of a saturated, aliphatic free glycol containing from 4 to 10 carbon atoms and having hydroxyl groups on its terminal carbon atoms, the molar amount of said polyester and said free glycol combined being essentially equivalent to the molar amount or" said diphenyl diisocyanate whereby there are essen tially no unreacted groups of the class consisting of isocyanate and hydroxyl groups in said elastomer.

12. The coating composition of claim 11 wherein said solution further includes polyoxyethylene sorbitan monooleate.

13. The coating composition of claim 11 wherein said member dissolved in water is gum tragacanth.

14. The coating composition of claim 11 wherein said member dissolved in Water is gum arabic.

15. The coating composition of claim 11 wherein said member dissolved in water is gum karaya.

16. The coating composition of claim 11 wherein said polyesterurethane is a linear hydroxyl terminated polyester produced by the reaction of hydroxyl poly (tetremethylene adipate) and butanediol-l,4, and said diisocyanate is diphenyl methaue-p,p-diisocyanate.

17. A method for making a water vapor permeable coated fabric comprising dispersing (A) flock in a mixture of (B) an aqueous solution of a gum selected from the group consisting of gum tragacanth, gum arabic and gum karaya and (C) a solution in an organic solvent comprising polyoxyethylene sorbitan monooleate and a vinylidene chloride-acrylonitrile copolymer, a major portion of which is vinylidene chloride, then applying said dispersion to the surface of a textile substrate, leaching said coated textile with water to remove the solvent and drying the coated fabric.

18. A coating composition comprising flock dispersed in a mixture of Water having dissolved therein a gum selected from the group consisting of gum tragacanth, gum karaya and gum arabic and a solution in an organic solvent comprising polyoxyethylene sorbitan monooleate and a vinylidene chloride-acrylonitrile copolymer a major portion of which is vinylidene chloride.

References Cited by the Examiner UNITED STATES PATENTS 2,751,363 6/56 Martin.

2,871,218 1/59 Schollenberger 26032.6 XR 3,085,896 4/63 Britt et al 11733 3,100,721 8/63 Holden 117-1355 WILLIAM D. MARTIN, Primary Examiner. RICHARD D. NEVIUS, Examiner. 

1. A METHOD FOR MAKING A WATER VAPOR PERMEABLE COATED FABRIC COMPRISING (A) FLOCK IN A MIXTURE OF (B) WATER HAVING DISSOLVED THEREIN A MEMBER SELECTED FROM THE GROUP CONSISTING OF CARBOXYMETHYL CELLULOSE, GUM ARABIC, GUM TRAGACANTH AND GUM KARAYA AND (C) A SOLUTION IN A SOLVENT, SELECTED FROM THE GROUP CONSISTING OF METHYL ETHYL KETONE, TETRAHYDROFURAN AND CYCLOHEXANONE, OF AN ESSENTIALLY LINEAR POLYESTERURETHANE ELASTOMER WHICH IS THE REACTION PRODUCT OBTAINED BY HEATING A MIXTURE COMPRISING AS ESSENTIAL POLYURETHANE INGREDIENTS (1) ONE MOL OF AN ESSENTIALLY LINEAR HYDROXYL TERMINATED POLYESTER OF A SATURATED ALIPHATIC GLYCOL HAVING FROM 4 TO 10 CARBON ATOMS AND HAVING HYDROXYL GROUPS ON ITS TERMINAL CARBON ATOMS AND A MATERIAL SELECTED FROM THE GROUP CONSISTING OF A DICARBOXYLIC ACID OF THE FORMULA 